As a biological waste treatment technique to purify organic waste (pollutant) such as industrial wastewater, sewage, night soil, leachate, kitchen waste, and animal manure by a microbial degradation potential of organic compounds, an activated sludge method, methane fermentation, and the like are known. In these biological waste treatments, the ability of a biological waste treatment facility is higher as microbial activity involved with decomposition of wastes is higher and the abundance of microorganisms is higher.
As a method for maintaining a useful microorganism at a high concentration in a reaction tank of a biological waste treatment facility, techniques such as an adhesion carrier method, an entrapping carrier method, a self-granulated sludge method, a biological membrane filtration method, and a membrane bio-reactor are developed (e.g., see Patent Literatures 1 and 2). With the use of these methods, the biological waste treatment can be performed in more compact facilities.
As another method for increasing microbial concentration, a method in which a microorganism having especially high decomposition activity of a pollutant to be treated is isolated from soil and separately pure-cultured, and then the microorganism is added into a reaction tank is also developed.
Further, Patent Literature 3 discloses use of a specific compound for adjusting a microbial signaling system.